The photosensitive regions of integrated circuits of an imager type can be regions of substrates of photodiodes, particularly SPADs (single photon avalanche diodes.)
This type of photodiode is notably used for detecting photons with a wavelength situated in the infrared (around 850 nm). This being the case, the quantum efficiency of these photodiodes is low for these wavelengths, whereas it is high for wavelengths in the visible domain. The signal-to-noise ratio of these photodiodes can therefore be poor.
It has therefore been proposed to use filters to reduce the detection of radiation in the visible domain which can be considered as noise for the operation of single photon avalanche diodes. This being the case, these filters are not always sufficiently effective.